Solar cells fabricated with various III-V compound semiconductors, such as galium arsenide (GaAs) and indium phosphide (InP), are generally well known in the solar cell art and have been fabricated with layers of both monocrystalline P-type and monocrystalline N-type materials to define the PN junction of the cell. Alternatively, these cells have been constructed using a combination of polycrystalline and monocrystalline semiconductor layers to form a PN heterojunction therebetween.
Examples of an all monocrystalline type of compound semiconductor solar cell are disclosed in Applied Physics Letters, Vol. 26, p. 457-467 (1975). An example of a combination monocrystalline-polycrystalline solar cell with a PN heterojunction is disclosed, for example, by S. Wagner et al in Applied Physics Letters No. 26, page 229 (1975).
While the above generally described cells represent some improvements relative to certain prior art solar cell fabrication techniques, their requirement for at least one monocrystalline semiconductor layer clearly limits the fabrication cost reduction of the cells as a result of the well-known refined process requirements for growing monocrystalline semiconductor materials. Therefore, because of the widespread interest in reducing the cost of solar cell fabrication while maintaining an acceptable conversion efficiency for same, the desirability to provide a commercially feasible all polycrystalline solar cell is manifest.